Seventy owl monkeys (Aotus triviragatus) were inoculated with JC virus, a human polyomavirus. An additional 22 monkeys were used as controls. Some of the animals were used to confirm our finding that two owl monkeys inoculated with JC virus developed brain tumors at 16 and 25 months postinoculation, respectively. Remaining animals were used in passage of the JC induced primary owl monkey tumor and variable routes of inoculations (single routes) instead of the multiple route in the original studies. The animals have been monitored for JC antibody. To date, most the virus inoculated animals have developed hemagglutination inhibition (HI) titers to JC virus.